WASHINGTON — A team of FBI agents has been conducting interviews in recent weeks in the Dominican Republic and the United States, looking into allegations that Sen. Robert Menendez, D-N.J., patronized prostitutes in the Caribbean nation, but has found no evidence to support the claim, according to two people familiar with the investigation.

One person said agents have asked about whether a Florida eye doctor — a close friend and major campaign donor to Menendez — provided the senator with prostitutes on vacations there. Another person said investigators are looking into allegations involving underage prostitutes and sex parties.

The two, who spoke on the condition of anonymity to discuss an active investigation, said FBI agents are following leads provided by an unknown tipster. In a series of e-mails with the FBI, the tipster alleged that the doctor, Salomon Melgen, had made prostitutes available to Menendez while he was staying at his friend’s resort home in the Dominican Republic. The tipster mentioned young prostitutes and prostitution parties.

The FBI agents are also examining the role Menendez played in advocating for a port security contract in the Dominican Republic that would benefit Melgen, two people familiar with the case said. Menendez has urged U.S. officials to put pressure on the Dominican government to enforce the dormant contract, saying enhanced port security is important for interdicting drug traffic. Melgen is an investor in the company holding the contract.

FBI spokesman Michael Leverock, of the bureau’s field office in Miami, declined to comment for this article.

Menendez has denied the prostitution allegations, calling them false “smears.”

“As we have said all along, Senator Menendez welcomes any review because his actions have been appropriate, and we believe the facts will confirm that,” a Menendez aide said Friday.

The staff member, who spoke on the condition of anonymity, said the senator’s efforts on behalf of the port deal were appropriate. “The senator has had a long history of advocating for increased port security across the world,” the aide said.

Melgen and his attorneys declined to comment on any criminal investigation.

The relationship between Menendez and Melgen has come under scrutiny in recent weeks. Menendez acknowledged this month that he had failed to properly disclose two trips he took in 2010 on Melgen’s private plane to Melgen’s villa, near the resort of Casa de Campo. The senator said he wrote Melgen a personal check for $58,500 to reimburse him for the plane rides last month. The Senate Ethics Committee is investigating the matter.

More in News

With his choice of restaurant executive Andrew Puzder to serve as his Labor secretary, President-elect Donald Trump has now tapped six big donors and fundraisers to serve in his administration, lining up an unprecedented concentration of wealthy backers for top posts.

Last month, Denver’s Department of Safety fired a deputy sheriff for using racial slurs and harassing inmates and a police sergeant for drinking while in uniform and abandoning a post to have sex with a woman.